Major changes to auto insurance regulations in 2010 "dramatically'' reduced benefits for drivers and turned out to be a huge "bonus'' for companies, added Horwath.

"In 2011, the value of statutory accident payouts fell by just under $2 billion, an astonishing 50 per cent reduction from 2010, but that same year Ontario's auto insurance rates still increased by five per cent,'' she told reporters.

"Fifteen per cent is reasonable when you consider that their payouts were reduced by 50 per cent.''

Drivers have yet to see any real reductions in their rates, so if the industry won't cut premiums voluntarily the government should mandate it through the provincial regulator, the Financial Services Commission of Ontario, added Horwath.

"The bottom line is if they're not prepared to change it, then yes, government will step in and say 'You must reduce your rates by 15 per cent within the upcoming year,''' she said.

"What I've said to the industry, and now I'm saying to the government, is it's time to get serious about the increasing rates in auto (insurance) and the non-realization of savings that should have happened over the last year or so.''

The Insurance Bureau of Canada did not immediately respond to requests for comment Monday on the NDP's demand for a 15 per cent reduction in premiums, which the party calculated would save the average Ontario driver about $226 a year.

Horwath also called Monday for $30 million in funding to eliminate home care waiting lists and institute a five-day guarantee for seniors who need home care, part of a growing set of NDP demands for premier-designate Kathleen Wynne.

About 6,100 Ontarians are on the waiting list for home care, and people can wait up to 262 days to receive the services they need in their home, said Horwath.

"Everyone agrees that home care is cost effective and makes a real difference in the life of seniors, yet we have a system that is not working as well as it should be,'' she said.

Last week, the NDP called on Wynne to close $1.3 billion in corporate tax loopholes, spend nearly $200 million on creating jobs for youth and call a public inquiry into the cancelled gas plants in Oakville and Mississauga, which cost taxpayers at least $230 million.

The NDP is not dictating what must be in the upcoming budget, insisted Horwath.

"I'm not saying these are the specific details that have to be in a budget, but I am saying we have a session upcoming and these things are very achievable and they need to be part of the government's plan for this session,'' she said.

"We want to see some movement on affordability matters, we want to see some movement on the health care system, some movement on youth jobs, but none of the movement can happen, in my opinion, if we don't have a real commitment to the accountability around the gas plants.''

Wynne said last week that she wouldn't want to see a government facing a $11.9-billion deficit spend millions more on a public inquiry, but she did not rule out a Conservative request to have a legislative committee study the cancelled gas plants.